CODEWITHSUNDEEP
c++iterator
Vincent
Vincent

Reputation: 60341

C++ : syntax for passing iterator to a function?

I am making a class which is a kind of container and I would like to make a constructor that can take a "first" and "last" iterator like std::vector and other standard containers. What would be the correct syntax ? (I want a template a function that can take any first/last iterator types available (like the standard library I think). Thank you very much !

As an example, I want something like that :

template<class ...> MyClass(... first, ... last)

But what are the ... ?

Thank you very much.

Regarding the first answer : I want a specific constructor that takes iterators as argument (because I have already constructors that take values and pointers as arguments)

EDIT : Is something like this ok ?

template<class T1, class T2> MyClass(std::iterator<T1, T2> first, std::iterator<T1, T2> last)

Upvotes: 4

Views: 8258

Answers (2)

D.Shawley
D.Shawley

Reputation: 59553

I think that you can do what you want by taking advantage of the fact that std::iterator's have a member named iterator_category. Combine this with SFINAE and you get something like the following:

#include <iostream>
#include <vector>

template <class X>
class my_class {
public:
    my_class(X a, X b) {
        std::cout << "in my_class(X,X)" << std::endl;
    }

    template <class Iter>
    my_class(Iter a, Iter b, typename Iter::iterator_category *p=0) {
        std::cout << "in my_class(Iter,Iter)" << std::endl;
    }
};

int
main()
{
    char buf[] = "foo";
    std::vector<char> v;

    my_class<int> one(1, 2);
    my_class<char*> two(&buf[0], &buf[3]);
    my_class<char> three(v.begin(), v.end());

    return 0;
}

This prints:

in my_class(X,X)
in my_class(X,X)
in my_class(Iter,Iter)

Upvotes: 3

Xeo
Xeo

Reputation: 131789

The ... can be whatever you want, it's just a placeholder name for whatever the type will be. I think you need to read a good book.

template<class Iter> MyClass(Iter first, Iter last)

Iter is a common name if the type should represent an iterator. Another option might be InIt to signal that the iterators should not be output iterators.

Upvotes: 6

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